Using more descriptive names for JWT parts.
Using more descriptive names for JWT parts.

Previous variables in verify_signed_jwt_with_certs did
not illustrate the actual use of each part.

google/oauth2client,jonparrott/oauth2client,google/oauth2client,clancychilds/oauth2client,googleapis/oauth2client,jonparrott/oauth2client,googleapis/oauth2client,clancychilds/oauth2client